The present invention relates to a foam material body for a mattress, and an element of furniture provided with the same.
Prior to the description of the present invention, it is believed to be advisable to define some terms which will be utilized hereinafter. In the field to which the present invention pertains, the terms "lower mattress" and "upper mattress" are frequently utilized. In an element of furniture utilized for lying and provided with spring transverse battens (which is called in Switzerland "lattlicouch"), the lower mattress is formed by a batten grate. when the term "mattress" is mentioned in the following description and claims, it is utilized to identify the upper mattress.
It is known to provide foam material bodies for mattresses with throughgoing openings and passages which extend transverse to the direction of elongation of the mattress, so as to influence the deformability and to provide ventilation of the mattress. One of such mattresses is disclosed for example in the German Offenlegungsschrift No. 2,841,870, which is the equivalent of U.S. Pat. No. 4,229,847, in which the foam material body is provided with a row of throughgoing openings extending transverse to the direction of elongation of the mattress. These throughgoing openings have an approximately lens-shaped cross-section whose larger portion is located in the horizontal central plane of the mattress, extends in the longitudinal direction of the mattress and is greater than the entire height of the foam material body. The maximum height of the throughgoing openings amounts to approximately two-thirds of the entire height of the foam material body. In the known foam material body, the center of the throughgoing openings and the greater dimension of the cross-section are located in the central plane of the foam material body. When the mattress bends along a vertical plane extending in its longitudinal direction, the neutral fiber of this bending is located in the above-mentioned central plane. The term "neutral fiber" is utilized here to define a fiber layer in which the material of the mattress neither stretches nor compresses during bending of the mattress. The throughgoing openings are located in the region of the neutral fiber and in the neighboring region. Thereby, no space is available in the upper and lower supporting faces of the foam material body, wherein the maximum elongation and shortening take place during the bending. The throughgoing openings increase the flexibility of the mattress only to a small extent. Since the throughgoing openings generally increase the flexibility only to a small extent, they must have relatively great cross-sectional dimensions. However, the throughgoing openings with such great cross-sectional dimensions have the disadvantage in the fact that during loading of the foam material body the latter has a tendency to assume a wave-like shape on the upper loaded side.
Another mattress is also known in which the foam material body is provided with recesses in its upper and lower supporting faces. Each recess in the upper supporting surface is arranged between two recesses provided in the lower supporting surface, and vice versa. Each recess has a mouth portion which is narrow and extends from the lower or upper supporting face normal to the latter, and an enlarged portion connected with the mouth portion at a certain depth. The enlarged portion is located approximately in the region of the central plane between the upper and lower supporting surfaces of the foam material body. When this mattress bends along a vertical plane extending in its longitudinal direction, the enlarged portions of the recesses are located in the vicinity of the neutral fiber, so that this increases the flexibility only to a small extent. The mouth portions of the recesses have practically no intermediate space available when the mattress assumes its horizontal unbent position. Thereby, the foam material body offers a relatively great resistance to bending, particularly in the region of that supporting face which dips during the bending.
A further known mattress has a three-layer foam material body. The outer layers are formed by compact plates without throughgoing openings or recesses. A core which is formed by the central layer is provided at its upper and lower supporting face with passages formed as recesses. These recesses which extend transverse to the direction of elongation of the mattress have a profile which is formed as a triangle with identical sides whose base line is straight and lies in the supporting face of the core and whose side lines form concave arcs. The recesses have, in their portions abutting against the outer layers, a relatively great width measured in direction of elongation of the mattress. Since the core is constituted of a harder foam material than the outer layers, the foam material body during loading by a person has a tendency to be considerably compressed in the region of the recesses, which is very disadvantageous.
The German Gebrauchsmuster No. 1,727,445 describes a three-layer mattress provided with upper and lower compact foam material plates and a foam material body therebetween, wherein the upper and lower sides of the intermediate foam material body is provided with mutually crossing recesses. The lower recess is located in the middle between two upper recesses. The foam material body provided with the recesses is straight in the longitudinal direction and in the transverse direction before insertion between the two outer foam material plates, so that the originally straight recesses become V-shaped. This mattress possesses disadvantages which are similar to the disadvantages of the above-described mattresses.